Process and apparatus for refrigeration by work-producing expansion



June 4, 1963 R. BECKER 3,091,941

PROCESS AND APPARATUS FOR REFRIGERATION BY WORK-PRODUCING EXPANSIONFiled June 16, 1958 2 Sheets-Sheet 1 fi Am a Mad Mada 1 June 4, 1963 RBECKER 3,091,941

PROCESS AND APPARATUS FOR REFRIGERATION BY WORK-PRODUCING EXPANSIONFiled June-l6, 1958 2 Sheets-Sheet 2 United States Patent 3,691,941PROtIESS AND APPARATUS FQR REFRIGERATIGN BY WURK-PRUDUCWG EXPANSEQNRudolf Becker, Munich-Selina, Germany, assiguor to Geselischaft fiirLindes Eismaschinen Alrtiengesellsehaft, Hollricgelskreuth, near Munich,Germany, a German company Filed June 16, 1958, Ser. No. 742,319 Claimspriority, application Germany .luly 4, 1957 6 Claims. (Cl. 6213) Theinvention concerns a process and a device for refrigeration bywork-producing expansion of a gas (or, gas mixture) which is cooled to alow temperature by means of a regenerator arrangement and thereafterliberated from the condensation products.

The present invention relates in particular to the fact that therefrigeration is effected in connection with a gas separation, which ispreferably carried out by low-temperature rectification. As is known,the gas to be expanded generally must be heated again before it entersthe expansion machine. Heretofore, special heating coils were used inthe regenerator for this purpose, but this expedient reduces theefiiciency of the regenerator. Another known possibility was to branchoff from the regenerator, at a central point, a partial gas currentwhich had not yet been cooled to the eventual extent, and to use thepartial gas current again for work-producing expansion. In this lattercase the gas had to be purified additionally by means of adsorbers. Useof such an adsorber, however, requires continuous supervision, andmoreover is expensive because of the necessary reversing device and alow temperature tank. If, on the other hand, an intermediate layer ofgel is used in the regenerator itself as an adsorbent, a poor carbondioxide adsorption was attained; and, respectively, increased switchinglosses were incurred, if the adsorption was effected at low temperature.Besides these disadvantages, the inherent shortcomings of the gel in theregenerator are considered generally as a considerable disadvantage.

The object of the present invention is to eliminate the above describeddisadvantages and to heat the gas flowing to the expansion machine witha good efiiciency of the regenerator and without any specialcomplications.

According to the invention the problem involved in refrigeration byWork-producing expansion of a gas (or, gas mixture) cooled to a lowtemperature by a regenerator arrangement and liberated from thecondensation products, e.g., carbon dioxide, Water and the like, whichgas (or, gas mixture) is heated before the expansion, is solved by theapplication of an additional regenerator, preferably interposed in thereversing operation of the regenerator arrangement, as a heat source forheating the gas or gas mixture respectively.

According to a special realization of the inventive concept, a part ofthe crude gas is branched off behind the regenerator arrangement, isconducted through the additional regenerator to be heated therein, andis fed to the expansion device. The expansion device used may be, andpreferably is, an expansion turbine.

Another realization of the inventive concept consists essentially inthat a separated component of the crude gas, obtained in a gasseparating devicein particular, a rectifying column arrangement-isconducted entirely or partly through the additional regenerator and thenis fed to the expansion device (e.g., turbine).

The gas, preheated in the above described manner according to theinvention, can-unless it is used completely and exclusively for therefrigeratiOn-be' added to another gas having a diiferent, preferablylower, temperature before it is introduced into the work-producingexpansion device; or, it can be used for the indirect heating of a gasto be expanded.

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Two embodiments of apparatus according to the invention are represented,by way of example, in the attached drawing, in which:

FIG. 1 is a schematic representation of a plant, embodying principles ofthe present invention, for the separation of nitrogen and oxygen fromair and illustrating the expansion of a crude gas through an expansionturbine; and

FIG. 2 is a schematic representation of a similarly constituted plantfor air rectification, showing a modification wherein one of theseparated gases, rather than the crude gas, is expanded through theturbine.

In FIG. 1, 1, 2, 3 and 4 designate two pairs of regenerators throughwhich compressed air is conducted, in known manner, from a compressor21, for cooling and cleaning. At 5 is denoted a two-stage rectifyingcolumn, into which is introduced the air issuing from the regeneratorarrangement at 6. In the valve position shown in the drawing, the airtraverses the regenerators 1 and 3, while the regenerators 2 and 4 arebeing traversed by the separation products. Nitrogen is taken from thehead of the column at '7 and issues at 8. Oxygen is taken from thecolumn 5 at outlet 9 and issues from the apparatus at 10. The sumpliquid of the pressure stage of column 5 is expanded, by way of line 22,into the upper, pressureless stage, while liquid compressed nitrogenflows through line 23 into the pressure-less stage of the column.

According to the invention an additional regenerator 11 is provided,which additional component is included in the reversing cycle of thevalves indicated by the usual symbols. A part of the pre-cleaned air isfirst branched oil from column 5 at outlet 12, then conducted by meansof lines 13 and 14, to and from the cold end of the regenerator ill forheating, followed by expansion in a known manner through air expansionturbine 15 and finally introduced at outlet 1-6 into the rectifyingcolumn arrangement in order to meet the cooling requirements of theseparating apparatus.

In the operation of the regenerator arrangement according to theinvention, the reversal of the re generators 1, 2 and 11, is so effectedthat each individual regenerator is first traversed by crude gas, thenscavenged by the separation component, and finally used for heating theturbine gas.

FIG. 2 shows by way of example a modified form, wherein not the crudegas (e.g., air) but rather one separation product thereof, particularlynitrogen, is expanded in the expansion turbine. The reference numbersare the same as in FIG. 1 for the identical parts. The air flow throughthe regenerators 1 and 3 is the same as in FIG. 1. However, in thepresent case all the air is introduced into the rectifying column 5 atoutlet 6. In order to meet the cooling requirements, nitrogen is takenfrom the head of the lower column at outlet 17 and is conducted throughthe expansion tur-bine 15, after which it flows in the represented valveposition through the regenerator 2. The heating of the turbine nitrogenis effected, according to this aspect of the invention, by means of aheat exchanger 18 which latter is traversed by a nitrogen current takenfrom the column 5 at outlet 7 and conducted, by way of lines 19 and 20,through the cold end of the regenerator 11 in order to be heated.

The decision through which end and what parts and zones respectively ofthe additional regenerator the gas to be heated shall be conducted,depends on the respective conditions encountered. Under certaincircumstancesit is possibleparticularly in an embodiment according toFIG. 2to significantly reduce the cross-section of the regenerators,e.g;, if necessary, to about half. Instead'of two large conventionalregenerators it is also possible in the arrangement according to theinvention to use three regenerators each of half the size.

It is to'be noted that the additional regenerator 1L1 can be used, ifthe circumstances make the same advantageous, at the same time toproduce a product of higher purity. To this end, separate outlets fornitrogen are provided in the regenerators 2 and 1121s indicated, forexample,in FIG. 2.

I claim:

1. In a process of refrigerating by the work performing expansion of acompressed gas, the method of heating the compressed gas in anarrangement of at least three cyclically alternated 'regenerators havingheat storing masses before the work performing expansion of the gas,which comprises:

in a first period leading a gas through a regenerator of saidarrangement from the Warm to the cold end thereof to cool the gas andcondense contaminants, in a second period leading a scavenging gasthrough said regenerator from the cold to the Warm end thereof to removea substantial part of the condensed contaminants from the heat storingmass thereof and in a third period warming the gas to be expanded andremoving the remaining condensed contaminants from said heat storingmass by transferring to said gas at least a part of the heat stored inthe heat storing mass of said regenerator by passing said gas in directcontact with said heat storing mass.

2. In a process of refrigerating by the work performing expansion of acompressed gas, the method of heating the compressed gas in anarrangement of at least three cyclically alternated regenerators havingheat storing masses before the work performing expansion whichcomprises:

in a first period leading a gas through a regenerator of saidarrangement from the Warm to the cold end thereof to cool the gas andcondense contaminants, in a second periodleading a scavenging gasthrough said regenerator from the cold to the Warm end thereof to removea substantial part of the condensed contaminants from the heat storingmass thereof and in a third period warming the gas to be expanded andremoving the remaining condensed contaminants from said heat storingmass by leading it through at least a part of said regenerator bypassing said gas in direct contact with said heat storing mass from thecold to the warm end thereof.

3. In a process of separating a gas mixture by rectification at lowtemperature comprising the work performing expansion of a compressed gasmixture, the method of heating the compressed gas mixture in anarrangement of at least three cyclically alternated regenerators havingheat storage masses before the expansion, which comprises:

in a first period leading the gas mixture to be separated through aregenerator of said arrangement from the warm to the cold end thereof tocool the gas mixture and condense contaminants, in a second period leading a separating fraction of said gas mixture through said regeneratorfrom the cold to the Warm end thereof to remove a substantial part ofthe condensed contaminants from the heat storing mass thereof and in athird period warming the gas mixture to be expanded and removing theremaining condensed contaminants from said heat storing mass by leadingthe gas mixture through at least a part of said regenerator from thecold to the warm end thereof in direct contact with said heat storingmass.

4. In a process of refrigerating by the Work performing expansion of acompressed gas, the method of heating the compressed gas in anarrangement of at least three cyclically alternated regenerators havingheat storing masses before the work performing expansion, whichcomprises:

in a first period leading a gas through a regenerator of saidarrangement from the warm to the cold end thereof to cool the gas andcondense contaminants, in a second period leading a scavenging gasthrough sm'd regenerator from the cold to the warm end thereof to removea substantial part of the condensed contaminants from the heat storingmass thereof and in a third period leading the gas cleaned and cooled inthe first period through at least a part of said regenerator from thecold to the warm end thereof to remove the remaining condensedcontaminants from said heat storing mass and to warm the gas andexpanding the gas to preform work.

5. Apparatus for refrigeration by means of the Work performing expansionof a gas in a low temperature system comprising an arrangement of atleast three cyclically alternated regenerators, each regeneratorincluding a heat storing mass and having only one steam-conducting crosssection and an outlet between its entrance and its exit ends, valvedconduit means for leading the gas to be expanded through a first of saidregenerators from the warm to the cold end thereof, to cool the gas andto condense contaminants, valved conduit means for leading a scavenginggas through a second of said regenerators from the cold to the warm endin direct contact With the heat storing mass thereof to remove asubstantial part of the con densed contaminants from the heat storingmass thereof, valved conduit means for leading the gas to be expandedfrom the cold end of said first regenerator to the cold end of a thirdof said regenerators, valved conduit means for leading the gas to beexpanded through at least a part of said third regenerator from the coldend thereof to said outlet between the entrance and the exit endsthereof and from said outlet directly to an expansion engine to 7 Warmand expand the gas and valve and conduit means to alternate said threeregenerators cyclically.

6. Apparatus as defined in claim 5 comprising a two stage rectifyingdevice, conduit means for leading at least a part of a cooled andcleaned gas mixture from the cold end of the first regenerator to thefoot of a high pressure column of said rectifying device, conduit meansfor leading an expanded gas mixture from the exit of the expansionengine to a low pressure column of said rectifying device, conduit meansfor leading a separating fraction as the scavenging gas from the top ofthe low pressure column to the cold end of the second regenerator.

References Cited in the file of this patent UNITED STATES PATENTS1,968,518 Fraser July 31, 1934 2,071,763 Pollitzer Feb. 23, 19372,084,334 Frankl June 22, 1937 2,603,956 Borchardt July 22, 19522,648,205 Hufn-agel Aug. 11, 1953 2,699,047 Karwat et al. Jan. 11, 19552,715,820 Becker Aug. 23, 1955 2,716,332 Haynes Aug. 30, 1955 2,737,784Becker et al. Mar. 13, 1956 2,763,137 Collins Sept. 18, 1956 2,765,637Etienne Oct. 9, 1956 2,788,646 Rice Apr. 16, 1957 2,825,212 Linde Mar.4, 1958 2,850,880 Jacob Sept. 9, 1958 2,863,295 Newton Dec. 9, 19582,866,321 Fuchs et al. Dec. 30, 1958 2,895,304 Wucherer et al. July 21,1959 2,915,880 Schuftan et al Dec. 8, 1959 2,918,801 First et al Dec.29, 1959 2,924,078 Tsunoda Feb. 9, 1960 2,955,434 Cost Oct. 11, 1960FOREIGN PATENTS 498,441 Canada Dec. 15, 1953 1,106,784 Germany May 18,1961 1,233,248 France May 2, 1960

1. IN A PROCESS OF REFRIGERATING BY THE WORK PERFORMING EXPANSION OF ACOMPRESSED GAS, THE METHOD OF HEATING THE COMPRESSED GAS IN ANARRANGEMENT OF AT LEAST THREE CYCLICALLY ALTERNATED REGENERATORS HAVINGHEAT STORING MASSES BEFORE THE WORK PERFORMING EXPANSION OF THE GAS,WHICH COMPRISES: IN A FIRST PERIOD LEADING A GAS THROUGH A REGENERATOROF SAID ARRANGEMENT FROM THE WARM TO THE COLD END THEREOF TO COOL THEGAS AND CONDENSE CONTAMINANTS, IN A SECOND PERIOD LEADING A SCAVENGINGGAS THROUGH SAID REGENERATOR FROM THE COLD TO THE WARM END THEREOF TOREMOVE A SUBSTANTIAL PART OF THE CONDENSED CONTAMINANTS FROM THE HEATSTORING MASS THEREOF AND IN A THIRD PERIOD WARMING THE GAS TO BEEXPANDED AND REMOVING THE REMAINING CONDENSED CONTAMINANTS FROM SAIDHEAT STORING MASS BY TRANSFERRING TO SAID GAS AT LEAST A PART OF THEHEAT STORED IN THE HEAT STORING MASS OF SAID REGENERATOR BY PASSING SAIDGAS IN DIRECT CONTACT WITH SAID HEAT STORING MASS.